Limits - Thunderbird

From MozillaZine Knowledge Base

(Difference between revisions)
Revision as of 21:53, 30 May 2012
Tanstaafl (Talk | contribs)
(global search)
<-- Previous diff
Revision as of 10:23, 31 May 2012
Wsm (Talk | contribs)
(Search results - global search references)
Next diff -->
Line 62: Line 62:
==Search results== ==Search results==
-Global search limits search results to 400 hits for performance reasons. [] Quick search (Ctrl+Shift+F) and the Quick Filter bar don't appear to have any limits. Any limits for "Search the web" (OpenSearch) would be imposed by the search provider.+Global search limits search results to 400 hits for performance reasons. [] [] []
 +Quick search (Ctrl+Shift+F) and the Quick Filter bar don't appear to have any limits. Any limits for "Search the web" (OpenSearch) would be imposed by the search provider.
==SMTP Servers== ==SMTP Servers==

Revision as of 10:23, 31 May 2012

This article describes the known limits. However, there is always the possibility of a configuration specific bug or a bug fix for a lower limit breaking in a maintenance release.



There is no known limit of the number of accounts you can have. If you run into one, it probably would be either a bug in how many accounts the folder pane can display or due to "Use Global Inbox" being checked for that account. One user mentioned using 90 accounts.

Address books

There is no known limit on the number of address books you can have or the number of addresses in an address book. (One user has 30,000 addresses spread across 63 address books. [1]) But for large numbers of contacts, at some point you might want to consider putting your contacts in an LDAP server.

Although there might not be limits on address book size or on the notes section in a card, you may easily encounter performance problems when you reach several thousand contacts or with large notes sizes. The reason is that for every addressbook that gets used while running Thunderbird, all the contacts in that address book are loaded into memory and stay in memory. This can result in general slowness of Thunderbird, not just slow address autocomplete. (One user reports a 4,265 KB address book of several contacts, including one with a 4.2MB note. It took a long time to switch to that address book or to switch between one of the normal cards and the one with a 4.2MB note. However, it didn't seem to effect auto-completion when composing a message.)


Thunderbird doesn't appear to impose any limit on the number of attachments or the maximum size of the attachment you can send in a message. Any limits are due to your e-mail provider or SMTP server. Note that sending a binary file as a attachment increases its size by a third due to base64 encoding sending two 8-bit characters as three 7-bit ASCII characters.

Thunderbird 1.5 is incompatible with Outlook in how it stores the filenames of attachments when they exceed 64 bytes. This article provides more information and a workaround.


Thunderbird disables cookies by default, but they can be useful for RSS and the Webmail and ThunderBrowse extensions. You can copy and reuse the cookies.txt file from your Firefox profile. Firefox defaults to a limit of 50 cookies per site and 1000 total, which you can change using network.cookie.maxPerHost and network.cookie.maxNumber . Since Thunderbird doesn't support those preferences the limit appears to be the default value in Firefox.

E-mail addresses

There appears to be a limit of approximately 60 addresses when sending messages if you enter each address separately. However, if you use lists (mail distribution lists) for most of the addresses any limit is imposed by whatever SMTP server you use.

You can receive messages sent to multiple addresses in the same mailbox. Any limitations would be due to your e-mail provider.

File descriptors

A file descriptor is a data structure used to access a file, normally only used with POSIX operating systems. Supposedly there is a hard coded limit in Thunderbird of 256 file descriptors under Solaris. If you open 256 different folders you'll run into that limit, even if you closed most of the folders. Nobody has mentioned a similar problem on other operating systems.

Folders and messages

IMAP folders have no effective size limit. (Thunderbird 3.1 added a 64-bit offset to the .msf file allowing folders larger than 4GB, if the file system permits that large a file. [2] [3]) However, using very large folders (3GB, 4GB, etc) is not recommended as compacting will take a long time, unless you have very fast disk.

Local Folders, including pop accounts, are limited to 4GB, until version 12. Thunderbird 12 adds support [4] for a "pluggable mail store", and also removes the 4GB local folder size.

Folders are stored as mbox format files in a profile folder on your boot disk by default. So normally you are limited to the amount of free space on your boot disk. However, you can use the Profile Manager to create a profile wherever you want (including on file shares). It's also possible to store folders outside of the profile, on any drive, in any directory. Pluggable storage previously mentioned allows for the possibility of storage formats other then Berkley mbox, and potentially removing the performance impact of compacting folders. However no storage types other the mbox currently exist.

Desktop search programs such as Google Desktop , Copernic or X1 may not be able to index the contents of a 4GB folder. X1 supposedly runs into problems at 1GB.

There is no known limit on the number of folders.


There are bug reports about some versions (mainly for OSX and some BSD systems) that accidentally lowered the maximum folder size to 2GB and some scenarios where Thunderbird doesn't check that adding a message will exceed the maximum folder size before it adds it.

Normally whether or not a folder is corrupted has no effect on the maximum size of the mbox file. However, in a very few cases the corruption caused Thunderbird to ignore the maximum file size, once reaching 35GB .

Folder hierarchies

The depth of the folder hierarchy is limited by the path to last folders header. That can't exceed the operating systems maximum path length (usually at least 255 characters). That is not the same as what you see in the folder pane, its includes the path to the parent folder in the profile (which might be over 100 characters), and five additional characters (back slash plus .sbd) for each child folder. If you run into this limit you can display more folders by moving the profile or the accounts directory closer to the root of the drive, so that less of the total path length is wasted. There is additional overhead if any of the folders have non-ASCII characters. For example, if its a IMAP account the server would send the string as modified UTF-7, which more than doubles the number of characters.

Thunderbird still has a very old bug (from 2004) that prevents it from displaying a child folder if the total length of the child folder's relative path exceeds 128 bytes. The relative path is the distance from the top (root) of the profile directory (not the total path length).

With local folders (POP accounts) you normally can't create a folder hierarchy that you can't fully use. However, that's not true for IMAP accounts since you could create it using webmail, and not be able to download all of the headers due to it exceeding the maximum path length. This limit doesn't apply to a Subscribe window in a IMAP account since it just lists what folders exist on the mail server (its not downloading headers).

Message Pane

If you use View -> Sort by -> Threaded and select more than 100 messages it will not list more than 100 conversations in the message pane. If you reach that limit you should see something like These messages take up: 14.4 MB. (Note: 287 messages are selected, the first 100 are shown) if you scroll to the bottom of the message pane.

Message filters and custom headers

The Mozilla message filter specification states you can create any number of custom headers and message filters. It doesn't state how many rules you can have. However, one of the source files has several error messages about a limit of 50 custom headers which one user has run into.

Multiple Identities

There is no known limit on the number of multiple identities (additional identities, not created due to creating an account). One user has 60. [5]

Search results

Global search limits search results to 400 hits for performance reasons. [6] [7] [8]

Quick search (Ctrl+Shift+F) and the Quick Filter bar don't appear to have any limits. Any limits for "Search the web" (OpenSearch) would be imposed by the search provider.

SMTP Servers

There is no known limit on the number of SMTP servers you can have. Unlike accounts, Thunderbird doesn't appear to test whether the additional SMTP server would be a duplicate.

Windows and tabs

The limits on the number of windows and tabs are not clear. There are what appear to be limits of eight compose message windows, ten content tabs, and ten web search tabs. However, you can create several dozen compose message windows. The limit of eight compose message windows occurs if you select several messages and then press Ctrl+R to reply to them. [9][10] [11] [12]

Limitations of Microsoft Windows

In some cases, Windows users may run into a hard limit placed on the maximum amount of characters any path can be. Symptoms may include, but aren't limited to, disappearing mail folders. The limit is usually a length of 260 characters unless an application supports UNICODE paths. Thunderbird doesn't appear to support UNICODE paths. [13]

See also

External links